Method for controlling a gearbox, a gearbox and a vehicle provided with such a gearbox

ABSTRACT

A method for controlling a gearbox that includes, a) shifting gear from a low range gear to a high range gear in the range gearbox ( 7 ); b) disconnecting a ring gear ( 54 ) of a planetary gear from a gearbox housing ( 52 ), synchronizing the speed between a third gear drive ( 74 ) on the main shaft ( 14 ) and the main shaft ( 14 ), connecting the third gear drive ( 74 ) and the main shaft ( 14 ); c) disconnecting a first part ( 14   a ) of the main shaft ( 14 ) from a second part ( 14   b ) of the main shaft ( 14 ), synchronizing the speed between a first gear wheel ( 64 ) and a lay shaft ( 22 ), connecting the first gear wheel ( 64 ) and the lay ( 22 ) shaft via a second and a third gear wheel ( 70, 76 ); and d) disconnecting the first, the second and the third gear wheels ( 64, 70, 76 ) and from the lay shaft ( 22 ), synchronizing the speed between the second part ( 14   b ) of the main shaft ( 14 ) and a planet carrier ( 38 ) of a planetary gear ( 37 ), connecting the second part ( 14   b ) of the main shaft ( 14 ) and the planet carrier ( 38 ); a gearbox ( 2 ), controlled by the method; and a vehicle ( 1 ) that comprises such a gearbox ( 2 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/SE2016/050937, filed Oct. 3, 2016, which claims priority of Swedish Patent Application No. 1551284-1, filed Oct. 6, 2015, the contents of all of which are incorporated herein by reference. The PCT International Application was published in the English language.

FIELD OF THE INVENTION

The present invention relates to a method for controlling a gearbox, a gearbox, a vehicle provided with such a gearbox, a computer program to control such a gearbox and a computer program product comprising program code according to the appended claims

BACKGROUND

In vehicles, and especially for heavier vehicles such as trucks, an auxiliary gearbox, also called a range gearbox, is often connected to a main gearbox to double the number of gears. Such an auxiliary gearbox usually includes a planetary gear, which has a low gear and a high gear, whereby the main gearbox shift facilities can be divided into a low range gear position and a high range gear position. In low range gear, a downshift takes place through the planetary gear, and, in the high range gear, the gear ratio is 1:1 in the planetary gear.

The range gearbox is usually provided between the main gearbox and a propeller shaft coupled to the drive wheels of the vehicle. The range gearbox is accommodated in a gearbox housing and comprises an input shaft coupled to the main gearbox and an output shaft coupled to the propeller shaft. Between the input shaft and the output shaft, the planetary gear is disposed. The planetary gear usually comprises three main components, which are rotatably arranged relative to each other. The three main components include a sun gear, a planet carrier with planet gears, and a ring gear. With knowledge of the number of teeth of the sun gear and the ring gear the relative speed of the three components can be determined during operation. In a range gearbox, the sun gear can be rotatably connected to the input shaft, a number of planet gears engage said sun gear and are rotatably mounted on the planet carrier, which is fixedly connected to the output shaft, and an axially displaceable ring gear surrounds and engages the planet gears.

In a known range gearbox, the low range gear position and the high range gear position are obtained by displacing the ring gear axially between the low range gear position, in which the ring gear is rotationally locked relative to the gearbox housing, and the high range gear position in which the ring gear is rotatable relative to the gearbox housing where the ring gear, the planet gears and the sun gear rotate as a common unit. The planetary gear comprises two coupling rings arranged on each side of the ring gear and two synchronizing rings arranged on each side of the ring gear. The synchronizer rings are arranged to provide a synchronous shift.

The document WO0155620 discloses a synchronization device in a planetary gear. The planetary gear includes a sun gear, a planet carrier and a ring gear. The sun gear is rotatably connected with the input shaft. A number of planet gears engage the sun gear and are rotatably mounted on the planet carrier, which is connected to the output shaft. An axially displaceable ring gear surrounds and meshes with the planet gears. Low and high gear are obtained by displacing the ring gear axially between the low range gear and the high range gear.

These synchronization means are subject to wear and are costly to repair. If the range gearbox is to transmit a large torque, the synchronization devices must be enlarged, which results in increased weight, increased space requirements and an increased moment of inertia.

There are range gearboxes in which the synchronization devices are replaced with coupling sleeves provided with splines. By controlling the transmission to synchronous speed between the two components to be connected it is possible to displace axially the coupling sleeve along the two components in order to connect the two components. When the components are to be detached, the transmission is controlled so that torque balance occurs between the components and the coupling sleeve is not transmitting torque. It then becomes possible to move the coupling sleeve along the components in order to disengage them from each other.

The document U.S. Pat. No. 6,196,944 shows a planetary gear comprising a sun gear, a planet carrier with planet gears and a ring gear. The sun gear may be connected to the input shaft by means of a coupling sleeve in a low range gear position and disengaged from the input shaft in a high range gear position. In the high range gear position the input shaft is connected to the planet carrier by means of the same coupling sleeve. The ring gear is firmly connected to a gearbox housing. The known planetary gear is arranged in an auxiliary gearbox, having only two gear positions.

The document U.S. Pat No. 6,196,944 shows a gearbox for motor vehicles comprising a planetary gear comprising a first and a second sleeve acting on the planet carrier, the ring gear, the gearbox housing and the output shaft. The first and second sleeves are controlled as one connected unit.

A gearbox provided with a double clutch system (also known as dual clutch system) comprises two or more input shafts, each connected to a clutch. The power from an energy source such as an internal combustion engine can be guided from one of the input shafts to the other by means of the clutch system, so that the power flow can be guided from one transmission shaft to a transmission shaft running in parallel, via gears meshing together.

Document US2014/0038769 A1 discloses a transmission using two transmission shafts running on axes parallel to each other, which can be coupled together. The transmission comprises a range gear.

However, when connecting a range gearbox to a main gearbox provided with a double clutch system it is difficult or even impossible to find a power flow through the transmission so that shifting gears can take place without an interruption of torque. An interruption of torque takes place in known gearboxes specially when shifting from a low range gear position to a high range gear position. A gearbox in which shifting of gears can take place without interruption of torque makes it possible to shift gears very fast, save fuel and provide comfort to the driver and the passengers of the vehicle in which the gearbox is arranged.

The space available for the powertrain in a vehicle is often limited. If the powertrain comprises several components, such as a combustion engine, a gearbox and a range gearbox, the design must be compact. At the same time, the components of the powertrain must be designed with dimensions that can absorb the necessary forces and torques.

A large number of gear steps are required in certain types of vehicles, in particular in heavy duty vehicles such as trucks and buses. In this case, the number of components of the gearbox increases, and the gearbox also must be dimensioned such that it can absorb large forces and torques, which arise in such heavy vehicles. Consequently, the size and the weight of the gearbox increase.

High demands are placed also on the reliability and the dependability, for the components of the powertrain. Wear influences the reliability and the lifetime of the gearbox.

SUMMARY OF THE INVENTION

There is a need to develop a method for controlling a gearbox that shifts gears without interruption in torque.

One object of the invention is to provide a method for controlling a gearbox that shifts gears without interruption in torque.

A further object of the invention is to provide a gearbox that has a compact design.

A further object of the invention is to provide a gearbox that has high reliability.

A further object of the invention is to provide a gearbox, which has low weight.

A further object of the invention is to provide a method to operate a gearbox which has a compact design, high reliability and/or low weight.

A further object of the invention is to provide an alternative gearbox and an alternative method to operate that gearbox.

These objects are achieved with a method for controlling a gearbox, a gearbox, a vehicle, a computer program for controlling a gearbox and a computer program product for controlling a gearbox according to the independent claims.

A method according to the invention allows for a gearbox that shifts gears without interruption in torque, which has a compact design, high reliability and low weight. According to the method there is no interruption in torque when shifting from a low range gear position to a high range gear position and vice versa.

It is preferable that the coupling elements comprise a ring shaped sleeve that is displaceable axially between its engaged and disengaged positions. The sleeve concentrically surrounds at least a part of the rotating components in the gearbox essentially and is displaced between the engaged and disengaged positions by means of a force provider. In this way, a compact design with low weight and low cost of manufacture is obtained.

The gearbox may be provided with a number of gear pairs that comprise gears which can be mechanically engaged and disengaged on shafts within the gearbox. In this way, a number of fixed gear steps are obtained, between which it is possible to shift gears without interruption in torque. The gear wheels that can be engaged on the shafts in the gearbox also result in a compact design with high reliability and high dependability.

Each one of the gear pairs has a gear ratio that is adapted to the desired driving performance of the vehicle. It is appropriate that the gear pair with the highest gear ratio, relative to the other gear pairs, is engaged when the lowest gear has been selected.

In order to disengage a gear from a shaft or from another gear, synchronizing elements are controlled such that torque balance is prevalent between the gear and the shaft or between the gears. When torque balance has been achieved, the sleeve is displaced such that the gear and the shaft, or the gears, are no longer mechanically connected to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described as an example below with reference to the attached drawings, of which:

FIG. 1 shows a schematic side view of a vehicle with a gearbox according to the invention,

FIG. 2 shows a schematic side view of the gearbox according to the invention,

FIG. 3 shows a view in detail of the synchronizing elements in FIG. 2,

FIG. 4 shows a shift pattern for shifting the gearbox according to the invention,

FIG. 5a shows a schematic view of the gearbox according to the invention in a first shifting step,

FIG. 5b shows a schematic view of the gearbox according to the invention in a second shifting step,

FIG. 5c shows a schematic view of the gearbox according to the invention in a third shifting step, and

FIG. 6 shows a flow diagram concerning a method of controlling the gearbox according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows schematically a vehicle 1 in a side view with a gearbox 2 according to the invention. The gearbox 2 is included in a powertrain 3, which comprises an internal combustion engine 4, a main gearbox 6, a range gearbox 7 and a propeller shaft 10. The combustion engine 4 is coupled to the main gearbox 6, which in turn is connected to the range gearbox 7. The range gearbox 7 is further connected to the drive wheels 8 of the vehicle 1 via the propeller shaft 10.

FIG. 2 shows a schematic sectional view of a gearbox 2 of the present invention. The gearbox 2 according to the invention comprises the main gearbox 6 and the range gearbox 7. The engine 4 is coupled to the gearbox 2 by means of a double clutch 12. The main gearbox 6 is provided with first and second synchronizing elements P1, P2, which are coupled to a main shaft 14 and a splitter shaft 16 in the gearbox 2. The main gearbox 6 comprises a main group 18 of gear pairs and a splitter group 20 of gear pairs upstream of the main group 18. The range gearbox 7 is arranged downstream of the main gearbox 6.

The main group 18 of gears of the main gearbox 6 comprises a first gear pair 60 that is arranged between the main shaft 14 and a lay shaft 22. The first gear pair 60 comprises a first gear wheel drive 62 and a first gear wheel 64, which interact with each other. A second gear pair 66 is arranged between the main shaft 14 and the lay shaft 22. The second gear pair 66 comprises a second gear wheel drive 68 and a second gear wheel 70, which interact with each other. A third gear pair 72 is arranged between the main shaft 14 and a lay shaft 22. The third gear pair 72 comprises a third gear wheel drive 74 and a third gear wheel 76, which interact with each other. A fourth gear pair 78 is arranged between the main shaft 14 and the lay shaft 44. The fourth gear pair 78 comprises a fourth gear wheel drive 80 and a fourth gear wheel 82, which interact with each other.

The first gear wheel drive 62 and the fourth gear wheel 82 are firmly attached to the main shaft 14 and the lay shaft 22, respectively, such that they cannot rotate relative to their respective shafts.

The lay shaft 22 extends essentially parallel to the main shaft 14. The second, the third and the fourth gear wheel drives 68, 74, 80 are arranged in bearings at the main shaft 14. The first, the second and the third gear wheels 64, 70, 76 are arranged in bearings at the lay shaft 22. The first gear wheel drive 62 interacts with the first gear wheel 64, the second gear wheel drive 68 interacts with the second gear wheel 70, the third gear wheel drive 74 interacts with the third gear wheel 76 and the fourth gear wheel drive 80 interacts with the fourth gear wheel 82.

The first, the second and the third gear wheels 64, 70, 76 can be engaged with and disengaged from each other with the aid of the first and the second coupling elements S1 and S2. The first, the second and the third gear wheels 64, 70, 76 can be engaged with and disengaged from the lay shaft 22 with the aid of the third coupling element S3.

The third gear wheel 76 can be individually engaged with and disengaged from the lay shaft 22 with the aid of the third coupling element S3. The second and the third gear wheel drives 68, 74 can be individually engaged and disengaged at the main shaft 14 with the aid of the fifth and the sixth coupling elements S5, S6. The fourth gear wheel drive 80 can be individually engaged and disengaged at a collar 41 which surrounds the main shaft 14. A fourth coupling element S4 is arranged to engage and disengage a first and a second part 14 a, 14 b of the main shaft 14. The coupling elements S1 to S3 and S5 to S8 are preferably constituted by sections equipped with splines designed at the gear wheels 64, 70, 76 and the gear wheel drives 68, 74, 80, and the main and the lay shafts 14, 22, respectively, which interact with the first to the third and the fifth to the eighth coupling sleeves 24-26, 28-31, which interact mechanically with the sections equipped with splines at the gear wheels 64, 70, 76 and gear wheel drives 68, 74, 80, respectively, and the main and the lay shafts 14, 22, respectively. A seventh coupling element S7 comprises a seventh coupling sleeve 30 for connecting the collar 41 with the main shaft 14 and for connecting and disconnecting a sun wheel 36 and a planet carrier 38 of a planetary gear 37 in the range gearbox 7. When in the disengaged condition, a relative rotation can arise between the gear wheels and the gear wheel drives 64, 70, 76, 68, 74 and 80, and the side and the main shafts 14, 22, respectively. The coupling element S4 is preferably also constituted by sections equipped with splines designed at an end part of the respective first and second parts 14 a, 14 b of the main shaft 14, which interact with a fourth coupling sleeve 27, which interact mechanically with the end parts of the respective first and second parts 14 a, 14 b of the main shaft 14. The coupling elements S1 to S8 may be constituted also by friction couplings. A ninth coupling element S9 comprising a ninth sleeve 32 is arranged to connect and disconnect a planet carrier shaft 40 from the collar 41. In an alternative example (not shown) a ninth coupling element S9 is not needed in the gearbox.

The splitter group 20 of the gears of the main gearbox 6 comprises a first splitter gear pair 42 that is arranged between the splitter shaft 16 and the lay shaft 22. The first splitter gear pair 42 comprises a first splitter gear wheel drive 43 and a first splitter gear wheel 44, which interact with each other. A second splitter gear pair 45 is arranged between the splitter shaft 16 and the lay shaft 22. The second splitter gear pair 45 comprises a second splitter gear wheel drive 46 and a second splitter gear wheel 47, which interact with each other.

The lay shaft 22 extends essentially parallel to the splitter shaft 16. The first and the second splitter gear wheel drives 43, 46 are attached to the splitter shaft 16. The first and the second splitter gear wheels 44, 47 are arranged in bearings at the lay shaft 22.

The first and the second splitter gear wheels 44, 47 can be individually engaged with and disengaged from the lay shaft 22 with the aid of a twelfth coupling element S12, comprising a twelfth sleeve 35, which is preferably constituted with splines interacting with sections equipped with splines arranged at the split gear wheels 44, 47 and the lay shaft 22, respectively. Preferably, the twelfth coupling element S12 is provided with a common coupling sleeve 35. When in the disengaged condition, a relative rotation can arise between the split gear wheels 44, 47 and the split gear wheel drives 43, 46 and the lay shaft 22. The twelfth coupling element S12 may be constituted also by a friction coupling.

The main shaft 14 extends inside a central bore in the splitter shaft 16. Thus, the main and splitter shafts 14, 16 are arranged coaxially. It is, however, also possible to arrange the main shaft 14 parallel to the splitter shaft 16.

The double clutch 12, which comprises first and second clutch elements 48, 49, is arranged between an engine shaft 50 and the main and splitter shafts 14, 16. The first clutch element 48 is connected to the main shaft 14 and the second clutch element 49 is connected to the splitter shaft 16. Torque generated by the engine 4 is guided from the engine shaft 50 to the main and the splitter shafts 14, 16 by means of the double clutch 12, so that the torque can be guided from the engine shaft 50 to an output shaft 51 of the range gearbox 7, via the different gears. The double clutch 12 is preferably a wet double clutch, but may also be implemented as a dry double clutch depending on the torque to be transmitted.

The range gearbox 7 aims to double the number of gear opportunities. The range gearbox 7 is surrounded by a gearbox housing 52. The range gearbox 7 comprises the planetary gear 37, which has a low and a high gear, so that the switching capability of the main gearbox 6 can be divided into a low range gear position and a high range gear position. In a first gear position, corresponding to the low range gear position, a downshift takes place in the planetary gear 37. In the high range gear position, the gear ratio is 1:1 in the planetary gear 37. In FIG. 2, the range gearbox 7 is shifted into a neutral position where the gearbox 7 does not transmit any torque from the input shaft 50 to the output shaft 51.

The planetary gear 37 comprises three main components which are rotatably arranged in relation to each other, namely a sun gear 36, a planet carrier 38 and a ring gear 54. A number of planet gears 53 are rotatably arranged with bearings on the planet carrier 38. With knowledge of the number of teeth of the sun gear 36 and the ring gear 54, the relative gear ratio of the three components can be determined. The sun gear 36 is rotatably connected to the main shaft 14 and the planet gears 53 engage the sun gear 36. The ring gear 54 surrounds and engages the planet gears 53.

A tenth coupling element S10, which comprises an axially displaceable tenth coupling sleeve 33, in the first gear position, is arranged to connect the gearbox housing 52 with the ring gear 54, and, in the second gear position is arranged to disconnect the gearbox housing 52 from the ring gear 54. An eleventh coupling element S11, which comprises an axially displaceable eleventh coupling sleeve 34, in the first and the second gear positions, is arranged to interconnect the planet carrier 38 with the output shaft 51.

The tenth coupling element S10, which comprises the axially displaceable tenth coupling sleeve 33, preferably includes first splines arranged on an inner surface to interact with the corresponding first splines arranged on the ring gear 54 and on the periphery of a projection 55, which is fixedly connected to the gearbox housing 52. The first splines on the axially displaceable tenth coupling sleeve 33 are also arranged to cooperate with corresponding first splines arranged on a first sprocket 56. Corresponding first splines on the axially displaceable tenth coupling sleeve 33 are also arranged to cooperate with corresponding first splines arranged on the planet carrier 38. Corresponding first splines disposed on the planet carrier 38 are arranged on the periphery of the first sprocket 56, which is mounted on the planet carrier 38.

An eleventh coupling element S11, which comprises an axially displaceable eleventh coupling sleeve 34, includes second splines on an inner surface arranged to cooperate with corresponding second splines arranged on the ring gear 54, the planet carrier 38 and the output shaft 51. The corresponding second splines arranged on the planet carrier 38 are formed on the periphery of a second sprocket 57, which is mounted on the planet carrier 38. The corresponding second splines provided on the output shaft 51 are formed on the periphery of a third sprocket 58, which is mounted on the output shaft 51.

The low gear in the range gearbox 7 is obtained by axially displacing the tenth coupling sleeve 33, so that the ring gear 54 is connected to the gearbox housing 52. The axial displacement of the tenth and the eleventh coupling sleeves 33, 34 can be provided by means of shift forks (not disclosed) partly arranged in an outside circumferential groove in the respective coupling sleeve 33, 34.

The range gearbox 7 according to the invention functions as follows when shifting from the first to the second gear position, that is, from the low range gear position to the high range gear position. In the low range gear position, the tenth coupling sleeve 33 has been shifted to a position to connect the ring gear 54 with the gearbox housing 52. Thus, when the range gearbox 7 is in the low range gear position, a downshift takes place through the planetary gear 37. The shifting operation from the low range gear position to the high range gear position is made by disconnecting the ring gear 54 from the gearbox housing 52 by means of the tenth coupling sleeve 33. Also, in the high range position the planet carrier 38 is connected to the main shaft 14 by means of the seventh coupling element S7. In order to again shift gear to the low range gear position, the tenth coupling sleeve 33 is shifted to connect the ring gear 54 with the gearbox housing 52.

The eleventh coupling sleeve 34 may be shifted into a third gear position in which the ring gear 54 is coupled to the output shaft 51, which is coupled to the propeller shaft 10 of the vehicle 1. In this gear position, corresponding to a reverse gear, the axially displaceable tenth coupling sleeve 33 is displaced to a position where the planet carrier 38 is connected to the gearbox housing 52.

The gearbox 2 is provided with a first and a second synchronizing element P1, P2 both connected to the main shaft 14 and to the splitter shaft 16 via gears of different ratios. The synchronizing elements P1, P2 are arranged to reduce or increase the speed of the main shaft 14 and the splitter shaft 16 in order to synchronize the speed of gears and shafts before shifting gears. The speed of the main shaft 14 and the splitter shaft 16 can be reduced or increased by means of the synchronizing elements P1, P2 since both the main shaft 14 and the splitter shaft 16 are connected to each synchronizing element P1, P2 and since the synchronizing elements P1, P2 are connected to the main shaft 14 and to the splitter shaft 16 via gears of different ratios. In FIG. 2, the second synchronizing element P2 is depicted with broken lines because the second synchronizing element P2 is hidden behind the splitter group 20 and the lay shaft 22. For reasons of clarity the lay shaft 22 has been removed in FIG. 3 and therefore the second synchronizing element P2 is clearly shown. Each synchronizing element P1, P2 is provided with a first and a second brake shaft 84, 85, which are connected to brake elements 86, such as friction brakes. A first synchronizing gear 87 on each synchronizing element P1, P2 is arranged to the first brake shaft 84, which interacts with a corresponding first synchronizing gear drive 88 on the splitter shaft 16. A second synchronizing gear 89 on each synchronizing element P1, P2 is arranged to the second brake shaft 85, which interacts with a corresponding second synchronizing gear drive 90 on the main shaft 14.

When shifting gears the power path from engine 4 to the output shaft 51 will be transferred through the main shaft 14 or the splitter shaft 16. Shifting of gears takes place on that of the shafts 14, 16 that does not transfer torque. When the next gear is shifted and prepared on that shaft 14/16 which does not transfer torque, the double clutch 12 is activated so that the power path from the engine 4 to the output shaft 51 will be transferred to the other shaft 14/16 on which the next gear is prepared.

The coupling elements S1, S2, . . . S12 are connected to a control unit 91 through the relevant coupling sleeves 24-35. Preferably, these components are activated and deactivated by electrical signals from the control unit 91. Preferably, the coupling sleeves 24-35 are displaced by force providers, not shown in the drawings, such as hydraulically or pneumatically powered cylinders. It is possible to displace the coupling sleeves 24-35 also by electrically powered force providers.

FIG. 4 shows a shift pattern of the gearbox 2 according to the invention. The shift pattern comprises fifteen forward gears which can be shifted and implemented without an interruption of torque through the gearbox 2. The neutral position in the shift pattern in FIG. 4 represents the position of the coupling elements S1, S2, . . . S12 in FIG. 2. Thus, the gearbox in FIG. 2 is in the neutral position and no torque is transferred from the engine 4 to the output shaft 51 of the gearbox 2.

From the shift pattern in FIG. 4 it is evident that three shift steps are performed when shifting from the eight gear to the ninth gear. These three shift steps are depicted 8>9a, 8>9b and 8>9c in the shift pattern.

In FIG. 5a the gearbox 2 is shifted in to the shift step 8>9a, in FIG. 5b the gearbox 2 is shifted in to the shift step 8>9b and in FIG. 5c the gearbox 2 is shifted in to the shift step 8>9c. In FIGS. 5a-5c the range gearbox 7 has been shifted to the second gear position or high range gear position in which the tenth coupling sleeve 33 of the tenth coupling element S10 had been shifted to a position where the ring gear 54 is disconnected from the gearbox housing 52. The transmission of torque from the engine shaft 50 to the output shaft 51 is in the high range gear position via the planet carrier 38 and further to the output shaft 51 via the eleventh coupling sleeve 34, so that the gear ratio through the planetary gear 37 becomes 1:1.

When shifting from the eighth gear to the ninth gear the first shift step 8>9a is performed by disconnecting the ring gear 54 of the planetary gear 37 from the gearbox housing 52 by means of a tenth coupling element S10. Thereafter, the speed between a third gear drive 74 on the main shaft 14 and the main shaft 14 is synchronized by means of activating the second synchronizing element P2, which decreases the speed of the main shaft 14. Finally, the third gear drive 74 and the main shaft 14 are connected by means of the sixth coupling element S6.

The second shift step 8>9b is performed by disconnecting the first part 14 a of the main shaft 14 from the second part 14 b of the main shaft 14 by means of the fourth coupling element S4. Thereafter, the speed between a first gear wheel 64 and a lay shaft 22 is synchronized by means of activating the first synchronizing element P1, which increases the speed of the main shaft 14. Finally, the first gear wheel 64 and the lay 22 shaft are connected via a second and a third gear wheel 70, 76 by means of the first coupling element S1.

The third shift step 8>9c is performed by disconnecting the first, the second and the third gear wheels 64, 70, 76 from the lay shaft 22 by means of the third coupling element S3. Thereafter, the speed between the second part 14 b of the main shaft 14 and a planet carrier 38 of a planetary gear 37 is synchronized by means of activating the second synchronizing element P2, which decreases the speed of the main shaft 14. Finally, the second part 14 b of the main shaft 14 and the planet carrier 38 are connected by means of the seventh coupling element S7.

When the third shift step 8>9c has been performed the splitter shaft 16 is disconnected from the engine 4 and the main shaft 14 is connect to the engine 4 by means of the double clutch 12.

FIG. 6 shows a flow diagram of a method of controlling the gearbox 2 according to the invention. The gearbox 2 comprises a main gearbox 6 provided with at least two input shafts in the form of a splitter shaft 16 and a main shaft 14, which are connectable to a power source 4, and a range gearbox 7 provided with a planetary gear 37, which is connectable to the main shaft 14.

The method according to the invention includes:

a) shifting a gear from a low range gear to a high range gear in the range gearbox 7;

b) disconnecting a ring gear 54 of the planetary gear from a gearbox housing 52, synchronizing the speed between a third gear drive 74 on the main shaft 14 and the main shaft 14, connecting the third gear drive 74 and the main shaft 14;

c) disconnecting a first part 14 a of the main shaft 14 from a second part 14 b of the main shaft 14, synchronizing the speed between a first gear wheel 64 and a lay shaft 22, connecting the first gear wheel 64 and the lay 22 shaft via a second and a third gear wheel 70, 76; and d) disconnecting the first, the second and the third gear wheels 64, 70, 76 from the lay shaft 22, synchronizing the speed between the second part 14 b of the main shaft 14 and a planet carrier 38 of a planetary gear 37, connecting the second part 14 b of the main shaft 14 and the planet carrier 38.

Preferably, the method further comprises:

e) disconnecting the splitter shaft 16 from the power source 4 and connecting the main shaft 14 to the power source 4.

Preferably, in step e), the disconnection of the splitter shaft 16 from the power source 4 and the connection of the main shaft 14 to the power source 4 is made by means of a double clutch 12.

Preferably, in step b), the ring gear 54 of the planetary gear 37 is disconnected from the gearbox housing 52 by means of a tenth coupling element S10.

Preferably, in step b), the speed between the third gear wheel drive 74 and the main shaft 14 is synchronized by means of activating a second synchronizing element P2, which decreases the speed of the main shaft 14.

Preferably, in step b), the third gear wheel drive 74 and the main shaft 14 are connected by means of a sixth coupling element S6.

Preferably, in step c), the first part 14 a of the main shaft 14 is disconnected from the second part 14 b of the main shaft 14 by means of a fourth coupling element S4.

Preferably, in step c), the speed between the first gear wheel 64 and the lay shaft 22 are synchronized by means of activating a first synchronizing element P1, which increases the speed of the main shaft 14.

Preferably, in step c), the first gear wheel 64 and the lay shaft 22 are connected by means of a first coupling element S1.

Preferably, in step d), the first, the second and the third gear wheels 64, 70 and 76 are disconnected from the lay shaft 22 by means of a third coupling element S3.

Preferably, in step d), the speed between the second part 14 b of the main shaft 14 and the planet carrier 38 is synchronized by means of activating the second synchronizing element P2, which decreases the speed of the main shaft 14.

Preferably, in step d), the second part 14 b of the main shaft 14 and the planet carrier 38 are connected by means of a seventh coupling element S7.

The electronic control unit 91 is coupled to the different components in the main gearbox 6, the range gearbox, the combustion engine 4 and the double clutch 12 to achieve the gear shifting above. Preferably, a number of (not shown) speed sensors in the main gearbox 6, the range gearbox 7, the combustion engine 4 and the double clutch 12 may be connected to the control unit 91. Another computer 92 may also be connected to the control unit 91. The control unit 91 may be a computer with appropriate software for this purpose. The control unit 91 and/or the computer 92 comprise a computer program P, which can include routines to control the gearbox 2 of the invention. The program P may be stored in an executable form or compressed form in a memory M and/or in a read/write memory. Preferably there is provided a computer program product comprising a program code stored on a computer readable medium for performing the gear shiftings above, when said program is run on the control unit 91 or another computer 92 connected to the control unit 91. Said code may be non-transitory and stored in said computer readable medium.

The specified components and distinctive features that are specified above may be combined between the different specified embodiments within the framework of the invention. 

The invention claimed is:
 1. A method for controlling a gearbox that includes a main gearbox provided with at least two input shafts, including a splitter shaft and a main shaft, which are connectable to a power source, and a range gearbox provided with the planetary gear, which is connectable to the main shaft, the method comprising: a) shifting gear from a low range gear to a high range gear in the range gearbox, the shifting gear from a low range gear to a high range gear in the range gearbox comprising, b) disconnecting a ring gear of the planetary gear from a gearbox housing, synchronizing a speed between a third gear drive on the main shaft and the main shaft, connecting the third gear drive and the main shaft; c) disconnecting a first part of the main shaft from a second part of the main shaft, synchronizing the speed between a first gear wheel and a lay shaft, connecting the first gear wheel and the lay shaft by a second and a third gear wheel; and d) disconnecting the first, the second and the third gear wheels from the lay shaft, synchronizing a speed between the second part of the main shaft and a planet carrier of the planetary gear, connecting the second part of the main shaft and the planet carrier.
 2. The method according to claim 1, further comprising, e) disconnecting the splitter shaft from the power source and connecting the main shaft to the power source.
 3. The method according to claim 2, wherein in step e), the disconnection of the splitter shaft from the power source and the connection of the main shaft to the power source is made by a double clutch.
 4. The method according to claim 1, wherein, in step b), the ring gear of the planetary gear is disconnected from the gearbox housing by a tenth coupling element.
 5. The method according to claim 1, wherein, in step b), the speed between the third gear drive and the main shaft is synchronized by activating a second synchronizing element, which decreases the speed of the main shaft.
 6. The method according to claim 1, wherein, in step b), the third gear drive and the main shaft are connected by means of a sixth coupling element.
 7. The method according to claim 1, wherein, in step c), the first part of the main shaft is disconnected from the second part of the main shaft by a fourth coupling element.
 8. The method according to claim 1, wherein, in step c), the speed between the first gear wheel and the lay shaft are synchronized by activating a first synchronizing element, which increases the speed of the main shaft.
 9. The method according to claim 1, wherein, in step c), the first gear wheel and the lay shaft are connected by a first coupling element.
 10. The method according to claim 1, wherein, in step d), the first, the second and the third gear wheels are disconnected from the lay shaft by a third coupling element.
 11. The method according to claim 1, wherein, in step d), the speed between the second part of the main shaft and the planet carrier is synchronized by activating the second synchronizing element, which decreases the speed of the main shaft.
 12. The method according to claim 1, wherein, in step d), the second part of the main shaft and the planet carrier are connected by a seventh coupling element.
 13. A gearbox comprising: a main gearbox provided with a splitter shaft having at least two input shafts and a main shaft, which are connectable to a power source; and a range gearbox provided with the planetary gear, which is connectable to the main shaft, wherein the gearbox is controllable by the method of claim
 1. 14. A vehicle comprising a gearbox according to claim
 13. 15. A computer product comprising: non-transitory program code stored on a medium that can be read by a computer in order to carry out the steps of claim 1, when the said program code is executed by an electronic control unit or another computer connected to the electronic control unit. 